The invention relates to a screw-type spindle press. More particularly, it relates to a screw type spindle press which has a housing including a spray casing and a screen casing defining an annular space therebetween, a press spindle rotatable in said housing within said screen casing so as to form a pressing space therebetween and provided with a plurality of wing members, and at least one axial zone which is free of the wing members, and at least one hollow perforated dewatering member which is provided in the above mentioned axial zone in the pressing space between the spindle and the screen casing and having an outlet in the annular space between the screen casing and the spray casing.
In a known pulp press of this type (DE-OS 31 25 653) the dewatering members, which are similar to the interruptors, are fastened directly at the housing, so that their hollow space is partly defined by means of the screen shell. Accordingly, dewatering surfaces are lost on the screen wall on the one hand and at the dewatering members on the other hand.
In another known pulp press of this type (DE Utility Model 1 846 103) interruptors are arranged in the axial zones between adjacent worm wings, which interruptors are guided through openings in the spray shell and the screen shell from the outside and are fastened at the spray shell. A hollow spindle body of the press spindle is perforated along its entire length for conducting the press fluid out of the pulp press cake.
The worm wings and the interruptors are provided with screen surfaces and with ducts for conducting out the press fluid. Details of the construction of the interruptors are not disclosed. It is disadvantageous that the length of the interruptors and, accordingly, their open cross-sectional surface area of flow-off decreases in a transporting direction of the pulp press.
Half-moon-shaped interruptors which are swivelable around their longitudinal axis are known, per se, from DE-PS 963 230; the pointed edge of these interruptors can be directed against the pulp flow. Every interruptor has a hollow space which communicates with the first annular space or pressing room via a series of nozzles in a rear wall of the interruptor. The nozzles serve to feed heat into the pressing room, particularly by means of steam for heating the pulp press when starting. The nozzles are also supposed to be suitable for conducting away the pressed out fluid. However, this appears to be ruled out, since the nozzles lie in an expansion area of the interruptor which decreases in cross-sectional surface area and in which the adjacent pressed pulp expands, that is, they release no fluid, but, on the contrary, suck it in. SUMMARY OF THE INVENTION
The invention has the object of increasing the output.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated in a screw press of the above mentioned general type in which the dewatering member or every one of the dewatering members is arranged at a radial distance from the spindle and the screen casing and is held by at least one carrier. The longitudinal axis of the screw press can be arranged so as to be vertical (upright) or horizontal (so as to lie) or can occupy any intermediate inclined position. With a circular cylindrical housing, the cross-sectional surface area of the spindle body preferably increases from the inlet side to the outlet side. Likewise, the pitch of the worm wings on the spindle body preferably decreases from the inlet side to the outlet side and the spindle body is hollow and perforated. As a rule, interruptors are fastened at the housing between adjacent worm wings so as to be distributed in a transverse plane and extend into the pressing room until the vicinity of the spindle body to the extent that this is allowed by the dewatering members. The radial distance of every dewatering member from the spindle body can be equal to its radial distance from the screen shell. The dewatering members preferably come to a point against the arriving material to be pressed. Accordingly, the division of the material flow along the dewatering member into material layers is facilitated. A considerable additional dewatering surface is provided by every dewatering member with respect to the material to be pressed which brushes past them. This is located in the interior of the material flow in the pressing room, that is, in a material zone which could otherwise only be insufficiently dewatered. The arrangement of the dewatering members thus contributes considerably to increasing the dry substance in the pressed material and to increasing the output of the screw press and, moreover, allows an effective removal of gas from the material to be pressed. The carrier can come to a point against the arriving material to be pressed in order to divide the material more easily in this manner and guide it around the carrier.
A particularly large additional dewatering surface can be provided if the dewatering member extends around the entire circumference of the press spindle. For this purpose the inner wall and the outer wall of every dewatering member can be formed as a circular cylindrical wall provided with a plurality of perforations and arranged concentrically to the longitudinal axis of the screw press or its press spindle.
In accordance with another feature of the present invention, a plurality of dewatering members can be arranged in every axial zone at a circumferential distance from one another, and an inner wall and an outer wall of every dewatering member can be formed as a segment of a circular cylinder provided with a plurality of perforations and arranged concentrically to the longitudinal axis of the screw press or its press spindle. In this construction axial webs of the material to be pressed remain between the dewatering members in the circumferential direction. These webs possess a certain shearing resistance and, in this way, act like interruptors which prevent the material to be pressed from rotating along with the press spindle.
It is still another feature of the present invention, that the outlet of the dewatering member can be integrated in the carrier. This feature is advantageous in terms of a simple construction. A plurality of carriers can be arranged at an axial distance from one another at every dewatering member. With this feature, unwanted deflecting movements of the dewatering members and their operating stresses are prevented.
A further feature of the present invention is that at least one rinsing line can be introduced into the dewatering member. The rinsing line can be connected with a rinsing fluid source by a connection line which is guided through the housing. Thereby the hollow space of each dewatering member can be cleaned in a simple manner. This can be effected, for example, with fresh water at a pressure of 3 to 6 bar when there is the risk that the perforations of the dewatering member will be impeded because of deposits or, e.g. stoppages with fibrous materials such as pulp.
The connection line of the above mentioned rinsing means can be formed as one of the carriers. This construction is structurally simple, wherein the carrier can again come to a point against the arriving material to be pressed.
The outlet of the dewatering member and the above mentioned connection line can be integrated together into one of the carriers. This construction also provides constructional advantages, wherein the carrier can again come to a point against the arriving material to be pressed.
Every dewatering member can be provided with a plurality of spacers located between its opposite walls. With this construction the distance between the opposite walls can also be maintained by simple means even under the external influence of pressure by means of the material to be pressed.
The housing of the screw press of the invention can be provided with a plurality of interruptors located radially outside of the dewatering member and introduced into the pressing space. These features can be used when there is the risk of the material to be pressed rotating along with the press spindle in the area of the dewatering members.